Cell culture vessels containing flexible, bag-type cell culture chambers can be difficult to manipulate if they are not supported by a rigid housing. If the flexible, bag-type cell culture chambers are supported by a tight-fitting rigid housing, the housing must also adjust to accommodate the expanding bag as it fills. If the housing is constructed so that it has a fixed capacity, then an under-filled bag will be free to move about within the housing during transport or other manipulations.
Growing large numbers of attachment dependent cells in bag-like cell culture devices is very difficult because the bags are inherently flexible. This characteristic compromises the ability of the cells to attach and decreases the possibility that the vessel can be manipulated robotically. To grow large numbers of cells, a large surface area is needed. Increasing the surface area of a bag-like device complicates handling. Stacking several smaller bag-like vessels typically requires a separate unit with shelves upon which the vessels can be supported. If the vessels are stacked to form an integral unit, a fixed volume is usually necessary to provide a rigid support. This abolishes the variable-volume benefit of having a bag-like device.
Most cell types may be cultured in bag-like cell culture devices. For example, cells such as cardiac, lung, muscle, bone and cartilage cells may be culture in such devices. Such cells when grown in vitro under conditions where some type of mechanical stress is applied to the cultured cells, differentiate to phenotypically resemble their in vivo counterparts. Without such an applied stress, such cells typically require soluble factors to differentiate. To induce differentiation via mechanical stress and strain, many researchers cobble together their own devices to provide the physical stimulus required to encourage cells to differentiate along a particular lineage. Commercially available devices for application of mechanical stress and strain tend to be very precise and limited to very small numbers of cells in culture.